The invention relates to object detection systems in general and, more particularly, to an object detection system and method with a self test operation.
Various object detection systems have been proposed to warn drivers of the presence of an object in the path of a movable vehicle. Typically, such warning system provide a suitable warning signal either audible or visual or both, upon detecting the presences of an object in the path of the moving vehicle.
In consideration of the importance of the operability of such object detection systems, it is often desirable for such systems to include self testing capabilities. For example, the co-pending U.S. patent application Ser. No. 07/758,244, now U.S. Pat. No. 5,160,927 issued to Cherry et al. describes an object detection system with a self test feature wherein object detection signals transmitted by the transmitter are received directly by the receiver for a self test check. Another object detection system with a self test feature is described in U.S. Pat. No. 4,910,512 issued to Riedel, in which signals provided by a transmitter are reflected by acoustic shunts or acoustic reflectors for reception by a receiver for self testing purposes. Furthermore, U.S. Pat. No. 4,561,064 to Bruggen et al. describes an object detection system with a self test feature in which a fixed reflector located on a vehicle reflects signals from the transmitter to the receiver to evaluate the system.
Conventional object detection systems with self testing capabilities represented by the above disclosures are dependent upon the use of signal reflectors being attached to the vehicle and/or the positioning of the transmitter and receiver on the vehicle so that parts of the vehicle do not interfere with the testing signals being transmitted from the transmitter to the receiver. Such systems may be undesirable due to the need for additional structures such as reflecting elements to be attached to the vehicle, and because the systems may require specific positioning of the transmitter and receiver in order to avoid transmission interference caused by preexisting structures on the vehicle.
It is accordingly an object of the present invention to provide an object detection system with a self test operation which does not require additional reflecting elements associated with the vehicle and/or specific positioning of the transmitter and receiver in order to avoid interference caused by preexisting structures on the vehicle.
It is a specific object of the present invention to provide an object detection system which operates to periodically adjust the system gain and/or detection threshold in order to allow the detection of low level signals reflected from irregularities in the ground surface which are used to self test the system.